Je souhaite lire des données XML à l'aide de XPath en Java. Par conséquent, je ne suis pas en mesure d'analyser XML en fonction de mes besoins.
voici ce que je veux faire:
Obtenir le fichier XML en ligne via son URL, puis utiliser XPath pour l'analyser, je veux créer deux méthodes en elle. La première consiste à entrer un ID d'attribut de nœud spécifique et à obtenir tous les nœuds enfants comme résultat; la deuxième est supposée si je veux juste obtenir une valeur de nœud enfant spécifique uniquement
<?xml version="1.0"?>
<howto>
<topic name="Java">
<url>http://www.rgagnonjavahowto.htm</url>
<car>taxi</car>
</topic>
<topic name="PowerBuilder">
<url>http://www.rgagnon/pbhowto.htm</url>
<url>http://www.rgagnon/pbhowtonew.htm</url>
</topic>
<topic name="Javascript">
<url>http://www.rgagnon/jshowto.htm</url>
</topic>
<topic name="VBScript">
<url>http://www.rgagnon/vbshowto.htm</url>
</topic>
</howto>
Dans l'exemple ci-dessus, je souhaite lire tous les éléments si je recherche via @name, ainsi qu'une fonction dans laquelle je souhaite simplement que l'URL de @name 'Javascript' ne renvoie qu'un élément de nœud.
Vous avez besoin de quelque chose dans le sens de ceci:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(<uri_as_string>);
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
XPathExpression expr = xpath.compile(<xpath_expression>);
Ensuite, vous appelez expr.evaluate()
en transmettant le document défini dans ce code et le type de retour attendu, puis convertissez le résultat en type d'objet du résultat.
Si vous avez besoin d'aide avec une expression XPath spécifique, vous devriez probablement la poser sous forme de questions distinctes (à moins que ce soit votre première question ici - j'ai compris que votre question était comment utiliser l'API en Java).
Edit: (Réponse au commentaire): Cette expression XPath vous obtiendrez le texte du premier élément URL sous PowerBuilder:
/howto/topic[@name='PowerBuilder']/url/text()
Cela vous donnera la seconde:
/howto/topic[@name='PowerBuilder']/url[2]/text()
Vous obtenez cela avec ce code:
expr.evaluate(doc, XPathConstants.STRING);
Si vous ne savez pas combien d'URL sont dans un nœud donné, vous devriez plutôt faire quelque chose comme ceci:
XPathExpression expr = xpath.compile("/howto/topic[@name='PowerBuilder']/url");
NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
Et puis boucle sur la NodeList.
Vous pouvez essayer ça.
Enregistrer sous employees.xml
.
<?xml version="1.0" encoding="UTF-8"?>
<Employees>
<Employee id="1">
<age>29</age>
<name>Pankaj</name>
<gender>Male</gender>
<role>Java Developer</role>
</Employee>
<Employee id="2">
<age>35</age>
<name>Lisa</name>
<gender>Female</gender>
<role>CEO</role>
</Employee>
<Employee id="3">
<age>40</age>
<name>Tom</name>
<gender>Male</gender>
<role>Manager</role>
</Employee>
<Employee id="4">
<age>25</age>
<name>Meghan</name>
<gender>Female</gender>
<role>Manager</role>
</Employee>
</Employees>
La classe a les méthodes suivantes
import Java.io.IOException;
import Java.util.ArrayList;
import Java.util.Arrays;
import Java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class Parser {
public static void main(String[] args) {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder;
Document doc = null;
try {
builder = factory.newDocumentBuilder();
doc = builder.parse("employees.xml");
// Create XPathFactory object
XPathFactory xpathFactory = XPathFactory.newInstance();
// Create XPath object
XPath xpath = xpathFactory.newXPath();
String name = getEmployeeNameById(doc, xpath, 4);
System.out.println("Employee Name with ID 4: " + name);
List<String> names = getEmployeeNameWithAge(doc, xpath, 30);
System.out.println("Employees with 'age>30' are:" + Arrays.toString(names.toArray()));
List<String> femaleEmps = getFemaleEmployeesName(doc, xpath);
System.out.println("Female Employees names are:" +
Arrays.toString(femaleEmps.toArray()));
} catch (ParserConfigurationException | SAXException | IOException e) {
e.printStackTrace();
}
}
private static List<String> getFemaleEmployeesName(Document doc, XPath xpath) {
List<String> list = new ArrayList<>();
try {
//create XPathExpression object
XPathExpression expr =
xpath.compile("/Employees/Employee[gender='Female']/name/text()");
//evaluate expression result on XML document
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++)
list.add(nodes.item(i).getNodeValue());
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return list;
}
private static List<String> getEmployeeNameWithAge(Document doc, XPath xpath, int age) {
List<String> list = new ArrayList<>();
try {
XPathExpression expr =
xpath.compile("/Employees/Employee[age>" + age + "]/name/text()");
NodeList nodes = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++)
list.add(nodes.item(i).getNodeValue());
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return list;
}
private static String getEmployeeNameById(Document doc, XPath xpath, int id) {
String name = null;
try {
XPathExpression expr =
xpath.compile("/Employees/Employee[@id='" + id + "']/name/text()");
name = (String) expr.evaluate(doc, XPathConstants.STRING);
} catch (XPathExpressionException e) {
e.printStackTrace();
}
return name;
}
}
Exemple de démarrage:
fichier xml:
<inventory>
<book year="2000">
<title>Snow Crash</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553380958</isbn>
<price>14.95</price>
</book>
<book year="2005">
<title>Burning Tower</title>
<author>Larry Niven</author>
<author>Jerry Pournelle</author>
<publisher>Pocket</publisher>
<isbn>0743416910</isbn>
<price>5.99</price>
</book>
<book year="1995">
<title>Zodiac</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553573862</isbn>
<price>7.50</price>
</book>
<!-- more books... -->
</inventory>
Code Java:
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
try {
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse (new File("c:\\tmp\\my.xml"));
// normalize text representation
doc.getDocumentElement().normalize();
System.out.println ("Root element of the doc is " + doc.getDocumentElement().getNodeName());
NodeList listOfBooks = doc.getElementsByTagName("book");
int totalBooks = listOfBooks.getLength();
System.out.println("Total no of books : " + totalBooks);
for(int i=0; i<listOfBooks.getLength() ; i++) {
Node firstBookNode = listOfBooks.item(i);
if(firstBookNode.getNodeType() == Node.ELEMENT_NODE) {
Element firstElement = (Element)firstBookNode;
System.out.println("Year :"+firstElement.getAttribute("year"));
//-------
NodeList firstNameList = firstElement.getElementsByTagName("title");
Element firstNameElement = (Element)firstNameList.item(0);
NodeList textFNList = firstNameElement.getChildNodes();
System.out.println("title : " + ((Node)textFNList.item(0)).getNodeValue().trim());
}
}//end of for loop with s var
} catch (SAXParseException err) {
System.out.println ("** Parsing error" + ", line " + err.getLineNumber () + ", uri " + err.getSystemId ());
System.out.println(" " + err.getMessage ());
} catch (SAXException e) {
Exception x = e.getException ();
((x == null) ? e : x).printStackTrace ();
} catch (Throwable t) {
t.printStackTrace ();
}
Voici un exemple de traitement de xpath avec vtd-xml ... pour un traitement XML intensif, sans pareil. voici un article récent sur ce sujet Traitement de XML avec Java - Benchmark de performances
import com.ximpleware.*;
public class changeAttrVal {
public static void main(String s[]) throws VTDException,Java.io.UnsupportedEncodingException,Java.io.IOException{
VTDGen vg = new VTDGen();
if (!vg.parseFile("input.xml", false))
return;
VTDNav vn = vg.getNav();
AutoPilot ap = new AutoPilot(vn);
XMLModifier xm = new XMLModifier(vn);
ap.selectXPath("/*/place[@id=\"p14\" and @initialMarking=\"2\"]/@initialMarking");
int i=0;
while((i=ap.evalXPath())!=-1){
xm.updateToken(i+1, "499");// change initial marking from 2 to 499
}
xm.output("new.xml");
}
}
Lire un fichier XML à l'aide de XPathFactory, SAXParserFactory
et StAX (JSR-173)
.
En utilisant XPath, obtenez le noeud et ses données enfants.
public static void main(String[] args) {
String xml = "<soapenv:Body xmlns:soapenv='http://schemas.xmlsoap.org/soap/envelope/'>"
+ "<Yash:Data xmlns:Yash='http://Yash.stackoverflow.com/Services/Yash'>"
+ "<Yash:Tags>Java</Yash:Tags><Yash:Tags>Javascript</Yash:Tags><Yash:Tags>Selenium</Yash:Tags>"
+ "<Yash:Top>javascript</Yash:Top><Yash:User>Yash-777</Yash:User>"
+ "</Yash:Data></soapenv:Body>";
String jsonNameSpaces = "{'soapenv':'http://schemas.xmlsoap.org/soap/envelope/',"
+ "'Yash':'http://Yash.stackoverflow.com/Services/Yash'}";
String xpathExpression = "//Yash:Data";
Document doc1 = getDocument(false, "fileName", xml);
getNodesFromXpath(doc1, xpathExpression, jsonNameSpaces);
System.out.println("\n===== ***** =====");
Document doc2 = getDocument(true, "./books.xml", xml);
getNodesFromXpath(doc2, "//person", "{}");
}
static Document getDocument( boolean isFileName, String fileName, String xml ) {
Document doc = null;
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(false);
factory.setNamespaceAware(true);
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(true);
DocumentBuilder builder = factory.newDocumentBuilder();
if( isFileName ) {
File file = new File( fileName );
FileInputStream stream = new FileInputStream( file );
doc = builder.parse( stream );
} else {
doc = builder.parse( string2Source( xml ) );
}
} catch (SAXException | IOException e) {
e.printStackTrace();
} catch (ParserConfigurationException e) {
e.printStackTrace();
}
return doc;
}
/**
* ELEMENT_NODE[1],ATTRIBUTE_NODE[2],TEXT_NODE[3],CDATA_SECTION_NODE[4],
* ENTITY_REFERENCE_NODE[5],ENTITY_NODE[6],PROCESSING_INSTRUCTION_NODE[7],
* COMMENT_NODE[8],DOCUMENT_NODE[9],DOCUMENT_TYPE_NODE[10],DOCUMENT_FRAGMENT_NODE[11],NOTATION_NODE[12]
*/
public static void getNodesFromXpath( Document doc, String xpathExpression, String jsonNameSpaces ) {
try {
XPathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
JSONObject namespaces = getJSONObjectNameSpaces(jsonNameSpaces);
if ( namespaces.size() > 0 ) {
NamespaceContextImpl nsContext = new NamespaceContextImpl();
Iterator<?> key = namespaces.keySet().iterator();
while (key.hasNext()) { // Apache WebServices Common Utilities
String pPrefix = key.next().toString();
String pURI = namespaces.get(pPrefix).toString();
nsContext.startPrefixMapping(pPrefix, pURI);
}
xpath.setNamespaceContext(nsContext );
}
XPathExpression compile = xpath.compile(xpathExpression);
NodeList nodeList = (NodeList) compile.evaluate(doc, XPathConstants.NODESET);
displayNodeList(nodeList);
} catch (XPathExpressionException e) {
e.printStackTrace();
}
}
static void displayNodeList( NodeList nodeList ) {
for (int i = 0; i < nodeList.getLength(); i++) {
Node node = nodeList.item(i);
String NodeName = node.getNodeName();
NodeList childNodes = node.getChildNodes();
if ( childNodes.getLength() > 1 ) {
for (int j = 0; j < childNodes.getLength(); j++) {
Node child = childNodes.item(j);
short nodeType = child.getNodeType();
if ( nodeType == 1 ) {
System.out.format( "\n\t Node Name:[%s], Text[%s] ", child.getNodeName(), child.getTextContent() );
}
}
} else {
System.out.format( "\n Node Name:[%s], Text[%s] ", NodeName, node.getTextContent() );
}
}
}
static InputSource string2Source( String str ) {
InputSource inputSource = new InputSource( new StringReader( str ) );
return inputSource;
}
static JSONObject getJSONObjectNameSpaces( String jsonNameSpaces ) {
if(jsonNameSpaces.indexOf("'") > -1) jsonNameSpaces = jsonNameSpaces.replace("'", "\"");
JSONParser parser = new JSONParser();
JSONObject namespaces = null;
try {
namespaces = (JSONObject) parser.parse(jsonNameSpaces);
} catch (ParseException e) {
e.printStackTrace();
}
return namespaces;
}
Document XML
<?xml version="1.0" encoding="UTF-8"?>
<book>
<person>
<first>Yash</first>
<last>M</last>
<age>22</age>
</person>
<person>
<first>Bill</first>
<last>Gates</last>
<age>46</age>
</person>
<person>
<first>Steve</first>
<last>Jobs</last>
<age>40</age>
</person>
</book>
Out mis pour le XPathExpression donné:
String xpathExpression = "//person/first";
/*OutPut:
Node Name:[first], Text[Yash]
Node Name:[first], Text[Bill]
Node Name:[first], Text[Steve] */
String xpathExpression = "//person";
/*OutPut:
Node Name:[first], Text[Yash]
Node Name:[last], Text[M]
Node Name:[age], Text[22]
Node Name:[first], Text[Bill]
Node Name:[last], Text[Gates]
Node Name:[age], Text[46]
Node Name:[first], Text[Steve]
Node Name:[last], Text[Jobs]
Node Name:[age], Text[40] */
String xpathExpression = "//Yash:Data";
/*OutPut:
Node Name:[Yash:Tags], Text[Java]
Node Name:[Yash:Tags], Text[Javascript]
Node Name:[Yash:Tags], Text[Selenium]
Node Name:[Yash:Top], Text[javascript]
Node Name:[Yash:User], Text[Yash-777] */
Voir ce lien pour notre propre implémentation de NamespaceContext
Cela vous montre comment
DOM
Nodes
avec XPath
Nodes
extraites. Nous appellerons le code avec la déclaration suivante
processFilteredXml(xmlIn, xpathExpr,(node) -> {/*Do something...*/;});
Dans notre cas, nous voulons imprimer une creatorNames
à partir d'un book.xml
en utilisant "//book/creators/creator/creatorName"
en tant que xpath pour exécuter une action printNode
sur chaque nœud correspondant à la XPath
.
Code complet
@Test
public void printXml() {
try (InputStream in = readFile("book.xml")) {
processFilteredXml(in, "//book/creators/creator/creatorName", (node) -> {
printNode(node, System.out);
});
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private InputStream readFile(String yourSampleFile) {
return Thread.currentThread().getContextClassLoader().getResourceAsStream(yourSampleFile);
}
private void processFilteredXml(InputStream in, String xpath, Consumer<Node> process) {
Document doc = readXml(in);
NodeList list = filterNodesByXPath(doc, xpath);
for (int i = 0; i < list.getLength(); i++) {
Node node = list.item(i);
process.accept(node);
}
}
public Document readXml(InputStream xmlin) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
return db.parse(xmlin);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private NodeList filterNodesByXPath(Document doc, String xpathExpr) {
try {
XPathFactory xPathFactory = XPathFactory.newInstance();
XPath xpath = xPathFactory.newXPath();
XPathExpression expr = xpath.compile(xpathExpr);
Object eval = expr.evaluate(doc, XPathConstants.NODESET);
return (NodeList) eval;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private void printNode(Node node, PrintStream out) {
try {
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.setOutputProperty("{http://xml.Apache.org/xslt}indent-amount", "2");
StreamResult result = new StreamResult(new StringWriter());
DOMSource source = new DOMSource(node);
transformer.transform(source, result);
String xmlString = result.getWriter().toString();
out.println(xmlString);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
Imprimés
<creatorName>Fosmire, Michael</creatorName>
<creatorName>Wertz, Ruth</creatorName>
<creatorName>Purzer, Senay</creatorName>
Pour book.xml
<book>
<creators>
<creator>
<creatorName>Fosmire, Michael</creatorName>
<givenName>Michael</givenName>
<familyName>Fosmire</familyName>
</creator>
<creator>
<creatorName>Wertz, Ruth</creatorName>
<givenName>Ruth</givenName>
<familyName>Wertz</familyName>
</creator>
<creator>
<creatorName>Purzer, Senay</creatorName>
<givenName>Senay</givenName>
<familyName>Purzer</familyName>
</creator>
</creators>
<titles>
<title>Critical Engineering Literacy Test (CELT)</title>
</titles>
</book>
Si vous avez un xml comme ci-dessous
<e:Envelope
xmlns:d = "http://www.w3.org/2001/XMLSchema"
xmlns:e = "http://schemas.xmlsoap.org/soap/envelope/"
xmlns:wn0 = "http://systinet.com/xsd/SchemaTypes/"
xmlns:i = "http://www.w3.org/2001/XMLSchema-instance">
<e:Header>
<Friends>
<friend>
<Name>Testabc</Name>
<Age>12121</Age>
<Phone>Testpqr</Phone>
</friend>
</Friends>
</e:Header>
<e:Body>
<n0:ForAnsiHeaderOperResponse xmlns:n0 = "http://systinet.com/wsdl/com/magicsoftware/ibolt/localhost/ForAnsiHeader/ForAnsiHeaderImpl#ForAnsiHeaderOper?KExqYXZhL2xhbmcvU3RyaW5nOylMamF2YS9sYW5nL1N0cmluZzs=">
<response i:type = "d:string">12--abc--pqr</response>
</n0:ForAnsiHeaderOperResponse>
</e:Body>
</e:Envelope>
et je voulais extraire le XML ci-dessous
<e:Header>
<Friends>
<friend>
<Name>Testabc</Name>
<Age>12121</Age>
<Phone>Testpqr</Phone>
</friend>
</Friends>
</e:Header>
Le code ci-dessous aide à atteindre le même
public static void main(String[] args) {
File fXmlFile = new File("C://Users//abhijitb//Desktop//Test.xml");
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
Document document;
Node result = null;
try {
document = dbf.newDocumentBuilder().parse(fXmlFile);
XPath xPath = XPathFactory.newInstance().newXPath();
String xpathStr = "//Envelope//Header";
result = (Node) xPath.evaluate(xpathStr, document, XPathConstants.NODE);
System.out.println(nodeToString(result));
} catch (SAXException | IOException | ParserConfigurationException | XPathExpressionException
| TransformerException e) {
e.printStackTrace();
}
}
private static String nodeToString(Node node) throws TransformerException {
StringWriter buf = new StringWriter();
Transformer xform = TransformerFactory.newInstance().newTransformer();
xform.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
xform.transform(new DOMSource(node), new StreamResult(buf));
return (buf.toString());
}
Maintenant, si vous voulez seulement le XML comme ci-dessous
<Friends>
<friend>
<Name>Testabc</Name>
<Age>12121</Age>
<Phone>Testpqr</Phone>
</friend>
</Friends>
Vous devez changer le
String xpathStr = "//Envelope//Header";
à String xpathStr = "//Envelope//Header/*";
En développant l'excellente réponse de @bluish et @Yishai, voici comment vous assurez que les attributs NodeLists et node prennent en charge les itérateurs, à savoir l'interface for(Node n: nodelist)
.
Utilisez-le comme:
NodeList nl = ...
for(Node n : XmlUtil.asList(nl))
{...}
et
Node n = ...
for(Node attr : XmlUtil.asList(n.getAttributes())
{...}
Le code:
/**
* Converts NodeList to an iterable construct.
* From: https://stackoverflow.com/a/19591302/779521
*/
public final class XmlUtil {
private XmlUtil() {}
public static List<Node> asList(NodeList n) {
return n.getLength() == 0 ? Collections.<Node>emptyList() : new NodeListWrapper(n);
}
static final class NodeListWrapper extends AbstractList<Node> implements RandomAccess {
private final NodeList list;
NodeListWrapper(NodeList l) {
this.list = l;
}
public Node get(int index) {
return this.list.item(index);
}
public int size() {
return this.list.getLength();
}
}
public static List<Node> asList(NamedNodeMap n) {
return n.getLength() == 0 ? Collections.<Node>emptyList() : new NodeMapWrapper(n);
}
static final class NodeMapWrapper extends AbstractList<Node> implements RandomAccess {
private final NamedNodeMap list;
NodeMapWrapper(NamedNodeMap l) {
this.list = l;
}
public Node get(int index) {
return this.list.item(index);
}
public int size() {
return this.list.getLength();
}
}
}